>> I wonder if there's a way to have the disk spinup at a slower
>> rate than usual ?
>> I guess that energy consumption is related to the
>> acceleration rate during the spinup phase, so spinning up at
>> a slower rate might help save a few watts (just a guess,
>> don't beat me if that's plain dumb).

> Physically speaking, it doesn't matter how fast or slow you
> speed up the disk. It takes the same energy. Faster spinup
> means higher power for a shorter time.
> The energy depends on the disk RPM (this is why 4200 RPM

It would be even worse to have a slower spinup. As Jörg
explained, the amount of energy needed to accelerate the disk
platters itself does not depend on how fast it is done. But in
real-world physics there is always friction, and if you would
have a slower spinup the disk would spin longer, rising the
enrgy loss generated by friction.